Inkjet nozzle arrangement having interleaved heater elements

ABSTRACT

An inkjet nozzle arrangement is provided having a wafer defining an ink chamber for holding ink and a chamber roof covering the ink chamber. The chamber roof has an ink ejection port supported by a plurality of outwardly extending bridge members and a plurality of elongate heater elements interleaved between the bridge members for causing ejection of ink held in the ink chamber through the ink ejection port.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/706,379 filed Feb. 15, 2007, now issued U.S. Pat. No. 7,520,593,which is a continuation application of U.S. application Ser. No.11/026,136 filed Jan. 3, 2005, now issued U.S. Pat. No. 7,188,933, whichis a continuation application of U.S. application Ser. No. 10/309,036filed Dec. 4, 2002, now issued U.S. Pat. No. 7,284,833, which is aContinuation Application of U.S. application Ser. No. 09/855,093 filedMay 14, 2001, now issued U.S. Pat. No. 6,505,912, which is aContinuation Application of U.S. application Ser. No. 09/112,806 filedJul. 10, 1998, now issued U.S. Pat. No. 6,247,790 all of which areherein incorporated by reference.

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, US patents/patent applications identified by their USpatent/patent application serial numbers are listed alongside theAustralian applications from which the US patents/patent applicationsclaim the right of priority.

U.S. Pat. No./ CROSS-REFERENCED patent application AUSTRALIAN (CLAIMINGRIGHT PROVISIONAL OF PRIORITY FROM PATENT AUSTRALIAN PROVISIONALAPPLICATION NO. APPLICATION) PO7991 6,750,901 PO8505 6,476,863 PO79886,788,336 PO9395 6,322,181 PO8017 6,597,817 PO8014 6,227,648 PO80256,727,948 PO8032 6,690,419 PO7999 6,727,951 PO8030 6,196,541 PO79976,195,150 PO7979 6,362,868 PO7978 6,831,681 PO7982 6,431,669 PO79896,362,869 PO8019 6,472,052 PO7980 6,356,715 PO8018 6,894,694 PO79386,636,216 PO8016 6,366,693 PO8024 6,329,990 PO7939 6,459,495 PO85016,137,500 PO8500 6,690,416 PO7987 7,050,143 PO8022 6,398,328 PO84977,110,024 PO8020 6,431,704 PO8504 6,879,341 PO8000 6,415,054 PO79346,665,454 PO7990 6,542,645 PO8499 6,486,886 PO8502 6,381,361 PO79816,317,192 PO7986 6,850,274 PO7983 09/113,054 PO8026 6,646,757 PO80286,624,848 PO9394 6,357,135 PO9397 6,271,931 PO9398 6,353,772 PO93996,106,147 PO9400 6,665,008 PO9401 6,304,291 PO9403 6,305,770 PO94056,289,262 PP0959 6,315,200 PP1397 6,217,165 PP2370 6,786,420 PO80036,350,023 PO8005 6,318,849 PO8066 6,227,652 PO8072 6,213,588 PO80406,213,589 PO8071 6,231,163 PO8047 6,247,795 PO8035 6,394,581 PO80446,244,691 PO8063 6,257,704 PO8057 6,416,168 PO8056 6,220,694 PO80696,257,705 PO8049 6,247,794 PO8036 6,234,610 PO8048 6,247,793 PO80706,264,306 PO8067 6,241,342 PO8001 6,247,792 PO8038 6,264,307 PO80336,254,220 PO8002 6,234,611 PO8068 6,302,528 PO8062 6,283,582 PO80346,239,821 PO8039 6,338,547 PO8041 6,247,796 PO8004 6,557,977 PO80376,390,603 PO8043 6,362,843 PO8042 6,293,653 PO8064 6,312,107 PO93896,227,653 PO9391 6,234,609 PP0888 6,238,040 PP0891 6,188,415 PP08906,227,654 PP0873 6,209,989 PP0993 6,247,791 PP0890 6,336,710 PP13986,217,153 PP2592 6,416,167 PP2593 6,243,113 PP3991 6,283,581 PP39876,247,790 PP3985 6,260,953 PP3983 6,267,469 PO7935 6,224,780 PO79366,235,212 PO7937 6,280,643 PO8061 6,284,147 PO8054 6,214,244 PO80656,071,750 PO8055 6,267,905 PO8053 6,251,298 PO8078 6,258,285 PO79336,225,138 PO7950 6,241,904 PO7949 6,299,786 PO8060 6,866,789 PO80596,231,773 PO8073 6,190,931 PO8076 6,248,249 PO8075 6,290,862 PO80796,241,906 PO8050 6,565,762 PO8052 6,241,905 PO7948 6,451,216 PO79516,231,772 PO8074 6,274,056 PO7941 6,290,861 PO8077 6,248,248 PO80586,306,671 PO8051 6,331,258 PO8045 6,110,754 PO7952 6,294,101 PO80466,416,679 PO9390 6,264,849 PO9392 6,254,793 PP0889 6,235,211 PP08876,491,833 PP0882 6,264,850 PP0874 6,258,284 PP1396 6,312,615 PP39896,228,668 PP2591 6,180,427 PP3990 6,171,875 PP3986 6,267,904 PP39846,245,247 PP3982 6,315,914 PP0895 6,231,148 PP0869 6,293,658 PP08876,614,560 PP0885 6,238,033 PP0884 6,312,070 PP0886 6,238,111 PP08776,378,970 PP0878 6,196,739 PP0883 6,270,182 PP0880 6,152,619 PO80066,087,638 PO8007 6,340,222 PO8010 6,041,600 PO8011 6,299,300 PO79476,067,797 PO7944 6,286,935 PO7946 6,044,646 PP0894 6,382,769

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to the field of fluid ejection and, inparticular, discloses a fluid ejection chip.

BACKGROUND OF THE INVENTION

Many different types of printing mechanisms have been invented, a largenumber of which are presently in use. The known forms of printers have avariety of methods for marking the print media with a relevant markingmedia. Commonly used forms of printing include offset printing, laserprinting and copying devices, dot matrix type impact printers, thermalpaper printers, film recorders, thermal wax printers, dye sublimationprinters and ink jet printers both of the drop on demand and continuousflow type. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles, has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques of ink jet printing have been invented. For asurvey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different forms. Theutilization of a continuous stream of ink in ink jet printing appears todate back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hanselldiscloses a simple form of continuous stream electro-static ink jetprinting.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including a step wherein the ink jet streamis modulated by a high frequency electro-static field so as to causedrop separation. This technique is still utilized by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat. No.3,373,437 by Sweet et al).

Piezoelectric ink jet printers are also one form of commonly utilizedink jet printing device. Piezoelectric systems are disclosed by Kyseret. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragmmode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) whichdiscloses a squeeze mode form of operation of a piezoelectric crystal,Stemme in U.S. Pat. No. 3,747,120 (1972) which discloses a bend mode ofpiezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 whichdiscloses a piezoelectric push mode actuation of the ink jet stream andFischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode typeof piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular formof ink jet printing. The ink jet printing techniques include thosedisclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S.Pat. No. 4,490,728. Both the aforementioned references disclose ink jetprinting techniques which rely on the activation of an electrothermalactuator which results in the creation of a bubble in a constrictedspace, such as a nozzle, which thereby causes the ejection of ink froman aperture connected to the confined space onto a relevant print media.Manufacturers such as Canon and Hewlett Packard manufacture printingdevices utilizing the electro-thermal actuator.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high-speed operation, safe and continuous long-termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction and operation, durability andconsumables.

Applicant has developed a substantial amount of technology in the fieldof micro-electromechanical inkjet printing. The parent application isindeed directed to a particular aspect in this field. In thisapplication, the Applicant has applied the technology to the moregeneral field of fluid ejection.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there isprovided a nozzle arrangement for an ink jet printhead, the arrangementcomprising a nozzle chamber defined in a wafer substrate for the storageof ink to be ejected; an ink ejection port having a rim formed on onewall of the chamber; and a series of actuators attached to the wafersubstrate, and forming a portion of the wall of the nozzle chamberadjacent the rim, the actuator paddles further being actuated in unisonso as to eject ink from the nozzle chamber via the ink ejection nozzle.

The actuators can include a surface which bends inwards away from thecenter of the nozzle chamber upon actuation. The actuators arepreferably actuated by means of a thermal actuator device. The thermalactuator device may comprise a conductive resistive heating elementencased within a material having a high coefficient of thermalexpansion. The element can be serpentine to allow for substantiallyunhindered expansion of the material. The actuators are preferablyarranged radially around the nozzle rim.

The actuators can form a membrane between the nozzle chamber and anexternal atmosphere of the arrangement and the actuators bend away fromthe external atmosphere to cause an increase in pressure within thenozzle chamber thereby initiating a consequential ejection of ink fromthe nozzle chamber. The actuators can bend away from a central axis ofthe nozzle chamber.

The nozzle arrangement can be formed on the wafer substrate utilizingmicro-electro mechanical techniques and further can comprise an inksupply channel in communication with the nozzle chamber. The ink supplychannel may be etched through the wafer. The nozzle arrangement mayinclude a series of struts which support the nozzle rim.

The arrangement can be formed adjacent to neighbouring arrangements soas to form a pagewidth printhead.

In this application, the invention extends to a fluid ejection chip thatcomprises

a substrate; and

a plurality of nozzle arrangements positioned on the substrate, eachnozzle arrangement comprising

-   -   a nozzle chamber defining structure which defines a nozzle        chamber and which includes a wall in which a fluid ejection port        is defined; and    -   at least one actuator for ejecting fluid from the nozzle chamber        through the fluid ejection port, the, or each, actuator being        displaceable with respect to the substrate on receipt of an        electrical signal, wherein    -   the, or each, actuator is formed in said wall of the nozzle        chamber defining structure, so that displacement of the, or        each, actuator results in a change in volume of the nozzle        chamber so that fluid is ejected from the fluid ejection port.

Each nozzle arrangement may include a plurality of actuators, eachactuator including an actuating portion and a paddle positioned on theactuating portion, the actuating portion being anchored to the substrateand being displaceable on receipt of an electrical signal to displacethe paddle, in turn, the paddles and the wall being substantiallycoplanar and the actuating portions being configured so that, uponreceipt of said electrical signal, the actuating portions displace thepaddles into the nozzle chamber to reduce a volume of the nozzlechamber, thereby ejecting fluid from the fluid ejection port.

A periphery of each paddle may be shaped to define a fluidic seal whenthe nozzle chamber is filled with fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIGS. 1-3 are schematic sectional views illustrating the operationalprinciples of the preferred embodiment;

FIG. 4( a) and FIG. 4( b) are again schematic sections illustrating theoperational principles of the thermal actuator device;

FIG. 5 is a side perspective view, partly in section, of a single nozzlearrangement constructed in accordance with the preferred embodiments;

FIGS. 6-13 are side perspective views, partly in section, illustratingthe manufacturing steps of the preferred embodiments;

FIG. 14 illustrates an array of ink jet nozzles formed in accordancewith the manufacturing procedures of the preferred embodiment;

FIG. 15 provides a legend of the materials indicated in FIGS. 16 to 23;and

FIG. 16 to FIG. 23 illustrate sectional views of the manufacturing stepsin one form of construction of a nozzle arrangement in accordance withthe invention.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the following description, reference is made to the ejection of inkfor application to ink jet printing. However, it will readily beappreciated that the present application can be applied to any situationwhere fluid ejection is required.

In the preferred embodiment, ink is ejected out of a nozzle chamber viaan ink ejection port using a series of radially positioned thermalactuator devices that are arranged about the ink ejection port and areactivated to pressurize the ink within the nozzle chamber therebycausing the ejection of ink through the ejection port.

Turning now to FIGS. 1, 2 and 3, there is illustrated the basicoperational principles of the preferred embodiment. FIG. 1 illustrates asingle nozzle arrangement 1 in its quiescent state. The arrangement 1includes a nozzle chamber 2 which is normally filled with ink so as toform a meniscus 3 in an ink ejection port 4. The nozzle chamber 2 isformed within a wafer 5. The nozzle chamber 2 is supplied with ink viaan ink supply channel 6 which is etched through the wafer 5 with ahighly isotropic plasma etching system. A suitable etcher can be theAdvance Silicon Etch (ASE) system available from Surface TechnologySystems of the United Kingdom.

A top of the nozzle arrangement 1 includes a series of radiallypositioned actuators 8, 9. These actuators comprise apolytetrafluoroethylene (PTFE) layer and an internal serpentine coppercore 17. Upon heating of the copper core 17, the surrounding PTFEexpands rapidly resulting in a generally downward movement of theactuators 8, 9. Hence, when it is desired to eject ink from the inkejection port 4, a current is passed through the actuators 8, 9 whichresults in them bending generally downwards as illustrated in FIG. 2.The downward bending movement of the actuators 8, 9 results in asubstantial increase in pressure within the nozzle chamber 2. Theincrease in pressure in the nozzle chamber 2 results in an expansion ofthe meniscus 3 as illustrated in FIG. 2.

The actuators 8, 9 are activated only briefly and subsequentlydeactivated. Consequently, the situation is as illustrated in FIG. 3with the actuators 8, 9 returning to their original positions. Thisresults in a general inflow of ink back into the nozzle chamber 2 and anecking and breaking of the meniscus 3 resulting in the ejection of adrop 12. The necking and breaking of the meniscus 3 is a consequence ofthe forward momentum of the ink associated with drop 12 and the backwardpressure experienced as a result of the return of the actuators 8, 9 totheir original positions. The return of the actuators 8,9 also resultsin a general inflow of ink from the channel 6 as a result of surfacetension effects and, eventually, the state returns to the quiescentposition as illustrated in FIG. 1.

FIGS. 4( a) and 4(b) illustrate the principle of operation of thethermal actuator. The thermal actuator is preferably constructed from amaterial 14 having a high coefficient of thermal expansion. Embeddedwithin the material 14 are a series of heater elements 15 which can be aseries of conductive elements designed to carry a current. Theconductive elements 15 are heated by passing a current through theelements 15 with the heating resulting in a general increase intemperature in the area around the heating elements 15. The position ofthe elements 15 is such that uneven heating of the material 14 occurs.The uneven increase in temperature causes a corresponding unevenexpansion of the material 14. Hence, as illustrated in FIG. 4( b), thePTFE is bent generally in the direction shown.

In FIG. 5, there is illustrated a side perspective view of oneembodiment of a nozzle arrangement constructed in accordance with theprinciples previously outlined. The nozzle chamber 2 is formed with anisotropic surface etch of the wafer 5. The wafer 5 can include a CMOSlayer including all the required power and drive circuits. Further, theactuators 8, 9 each have a leaf or petal formation which extends towardsa nozzle rim 28 defining the ejection port 4. The normally inner end ofeach leaf or petal formation is displaceable with respect to the nozzlerim 28. Each activator 8, 9 has an internal copper core 17 defining theelement 15. The core 17 winds in a serpentine manner to provide forsubstantially unhindered expansion of the actuators 8, 9. The operationof the actuators 8, 9 is as illustrated in FIG. 4( a) and FIG. 4( b)such that, upon activation, the actuators 8 bend as previously describedresulting in a displacement of each petal formation away from the nozzlerim 28 and into the nozzle chamber 2. The ink supply channel 6 can becreated via a deep silicon back edge of the wafer 5 utilizing a plasmaetcher or the like. The copper or aluminum core 17 can provide acomplete circuit. A central arm 18 which can include both metal and PTFEportions provides the main structural support for the actuators 8, 9.

Turning now to FIG. 6 to FIG. 13, one form of manufacture of the nozzlearrangement 1 in accordance with the principles of the preferredembodiment is shown. The nozzle arrangement 1 is preferably manufacturedusing micro-electromechanical (MEMS) techniques and can include thefollowing construction techniques:

As shown initially in FIG. 6, the initial processing starting materialis a standard semi-conductor wafer 20 having a complete CMOS level 21 toa first level of metal. The first level of metal includes portions 22which are utilized for providing power to the thermal actuators 8, 9.

The first step, as illustrated in FIG. 7, is to etch a nozzle regiondown to the silicon wafer 20 utilizing an appropriate mask.

Next, as illustrated in FIG. 8, a 2 μm layer of polytetrafluoroethylene(PTFE) is deposited and etched so as to define vias 24 forinterconnecting multiple levels.

Next, as illustrated in FIG. 9, the second level metal layer isdeposited, masked and etched to define a heater structure 25. The heaterstructure 25 includes via 26 interconnected with a lower aluminum layer.

Next, as illustrated in FIG. 10, a further 2 μm layer of PTFE isdeposited and etched to the depth of 1 μm utilizing a nozzle rim mask todefine the nozzle rim 28 in addition to ink flow guide rails 29 whichgenerally restrain any wicking along the surface of the PTFE layer. Theguide rails 29 surround small thin slots and, as such, surface tensioneffects are a lot higher around these slots which in turn results inminimal outflow of ink during operation.

Next, as illustrated in FIG. 11, the PTFE is etched utilizing a nozzleand actuator mask to define a port portion 30 and slots 31 and 32.

Next, as illustrated in FIG. 12, the wafer is crystallographicallyetched on a <111> plane utilizing a standard crystallographic etchantsuch as KOH. The etching forms a chamber 33, directly below the portportion 30.

In FIG. 13, the ink supply channel 34 can be etched from the back of thewafer utilizing a highly anisotropic etcher such as the STS etcher fromSilicon Technology Systems of United Kingdom. An array of ink jetnozzles can be formed simultaneously with a portion of an array 36 beingillustrated in FIG. 14. A portion of the printhead is formedsimultaneously and diced by the STS etching process. The array 36 shownprovides for four column printing with each separate column attached toa different color ink supply channel being supplied from the back of thewafer. Bond pads 37 provide for electrical control of the ejectionmechanism.

In this manner, large pagewidth printheads can be fabricated so as toprovide for a drop-on-demand ink ejection mechanism.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet printheads operating in accordance with theprinciples taught by the present embodiment can proceed utilizing thefollowing steps:

1. Using a double-sided polished wafer 60, complete a 0.5 micron, onepoly, 2 metal CMOS process 61. This step is shown in FIG. 16. Forclarity, these diagrams may not be to scale, and may not represent across section though any single plane of the nozzle. FIG. 15 is a key torepresentations of various materials in these manufacturing diagrams,and those of other cross-referenced ink jet configurations.

2. Etch the CMOS oxide layers down to silicon or second level metalusing Mask 1. This mask defines the nozzle cavity and the edge of thechips. This step is shown in FIG. 16.

3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treatthe surface of this polymer for PTFE adherence.

4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE) 62.

5. Etch the PTFE and CMOS oxide layers to second level metal using Mask2. This mask defines the contact vias for the heater electrodes. Thisstep is shown in FIG. 17.

6. Deposit and pattern 0.5 microns of gold 63 using a lift-off processusing Mask 3. This mask defines the heater pattern. This step is shownin FIG. 18.

7. Deposit 1.5 microns of PTFE 64.

8. Etch 1 micron of PTFE using Mask 4. This mask defines the nozzle rim65 and the rim at the edge 66 of the nozzle chamber. This step is shownin FIG. 19.

9. Etch both layers of PTFE and the thin hydrophilic layer down tosilicon using Mask 5. This mask defines a gap 67 at inner edges of theactuators, and the edge of the chips. It also forms the mask for asubsequent crystallographic etch. This step is shown in FIG. 20.

10. Crystallographically etch the exposed silicon using KOH. This etchstops on <111> crystallographic planes 68, forming an inverted squarepyramid with sidewall angles of 54.74 degrees. This step is shown inFIG. 21.

11. Back-etch through the silicon wafer (with, for example, an ASEAdvanced Silicon Etcher from Surface Technology Systems) using Mask 6.This mask defines the ink inlets 69 which are etched through the wafer.The wafer is also diced by this etch. This step is shown in FIG. 22.

12. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink to the ink inlets 69 at the back of the wafer.

13. Connect the printheads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

14. Fill the completed print heads with ink 70 and test them. A fillednozzle is shown in FIG. 23.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic“minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However, presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

High-resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table below under the heading CrossReferences to Related Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5-micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The printheads each contain 19,200 nozzles plus data andcontrol circuitry.

Ink is supplied to the back of the printhead by injection molded plasticink channels. The molding requires 50 micron features, which can becreated using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 above which matches the docket numbers in the table under theheading Cross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet printheads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixis set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) DescriptionAdvantages Disadvantages Examples Thermal An electrothermal Large HighCanon bubble heater heats the force generated power Bubblejet 1979 inkto above Simple Ink carrier Endo et al GB boiling point, constructionlimited to water patent 2,007,162 transferring No Low Xerox significantheat to moving parts efficiency heater-in-pit the aqueous ink. A FastHigh 1990 Hawkins et bubble nucleates operation temperatures al U.S.Pat. No. and quickly forms, Small chip required 4,899,181 expelling theink. area required for High Hewlett- The efficiency of actuatormechanical Packard TIJ the process is low, stress 1982 Vaught et withtypically less Unusual al U.S. Pat. No. than 0.05% of the materials4,490,728 electrical energy required being transformed Large intokinetic energy drive transistors of the drop. Cavitation causes actuatorfailure Kogation reduces bubble formation Large print heads aredifficult to fabricate Piezo- A piezoelectric Low Very large Kyser et alelectric crystal such as power area required for U.S. Pat. No. 3,946,398lead lanthanum consumption actuator Zoltan zirconate (PZT) is Many inkDifficult U.S. Pat. No. 3,683,212 electrically types can be to integratewith 1973 activated, and used electronics Stemme U.S. Pat. No. eitherexpands, Fast High 3,747,120 shears, or bends to operation voltage driveEpson apply pressure to High transistors Stylus the ink, ejectingefficiency required Tektronix drops. Full IJ04 page width print headsimpractical due to actuator size Requires electrical poling in highfield strengths during manufacture Electro- An electric field is Low LowSeiko strictive used to activate power maximum strain Epson, Usui etelectrostriction in consumption (approx. 0.01%) all JP 253401/96 relaxormaterials Many ink Large area IJ04 such as lead types can be requiredfor lanthanum used actuator due to zirconate titanate Low low strain(PLZT) or lead thermal Response magnesium expansion speed is niobate(PMN). Electric marginal (~10 μs) field strength High required voltagedrive (approx. 3.5 V/μm) transistors can be required generated Fullwithout page width print difficulty heads Does not impractical duerequire electrical to actuator size poling Ferro- An electric field isLow Difficult IJ04 electric used to induce a power to integrate withphase transition consumption electronics between the Many ink Unusualantiferroelectric types can be materials such as (AFE) and used PLZSnTare ferroelectric (FE) Fast required phase. Perovskite operation (<1 μs)Actuators materials such as Relatively require a large tin modified leadhigh longitudinal area lanthanum strain zirconate titanate High (PLZSnT)exhibit efficiency large strains of up Electric to 1% associated fieldstrength of with the AFE to around 3 V/μm FE phase can be readilytransition. provided Electro- Conductive plates Low Difficult IJ02, IJ04static are separated by a power to operate plates compressible orconsumption electrostatic fluid dielectric Many ink devices in an(usually air). Upon types can be aqueous application of a usedenvironment voltage, the plates Fast The attract each other operationelectrostatic and displace ink, actuator will causing drop normally needto ejection. The be separated conductive plates from the ink may be in acomb Very large or honeycomb area required to structure, or achieve highstacked to increase forces the surface area High and therefore thevoltage drive force. transistors may be required Full page width printheads are not competitive due to actuator size Electro- A strongelectric Low High 1989 Saito static pull field is applied to currentvoltage required et al, U.S. Pat. No. on ink the ink, whereuponconsumption May be 4,799,068 electrostatic Low damaged by 1989 Miuraattraction temperature sparks due to air et al, U.S. Pat. No.accelerates the ink breakdown 4,810,954 towards the print RequiredTone-jet medium. field strength increases as the drop size decreasesHigh voltage drive transistors required Electrostatic field attractsdust Permanent An electromagnet Low Complex IJ07, IJ10 magnet directlyattracts a power fabrication electro- permanent magnet, consumptionPermanent magnetic displacing ink and Many ink magnetic causing droptypes can be material such as ejection. Rare used Neodymium Iron earthmagnets with Fast Boron (NdFeB) a field strength operation required.around 1 Tesla can High High local be used. Examples efficiency currentsrequired are: Samarium Easy Copper Cobalt (SaCo) and extension frommetalization magnetic materials single nozzles to should be used in theneodymium page width print for long iron boron family headselectromigration (NdFeB, lifetime and low NdDyFeBNb, resistivityNdDyFeB, etc) Pigmented inks are usually infeasible Operatingtemperature limited to the Curie temperature (around 540 K) Soft Asolenoid Low Complex IJ01, IJ05, magnetic induced a power fabricationIJ08, IJ10, IJ12, core magnetic field in a consumption Materials IJ14,IJ15, IJ17 electro- soft magnetic core Many ink not usually magnetic oryoke fabricated types can be present in a from a ferrous used CMOS fabsuch material such as Fast as NiFe, electroplated iron operation CoNiFe,or CoFe alloys such as High are required CoNiFe [1], CoFe, efficiencyHigh local or NiFe alloys. Easy currents required Typically, the softextension from Copper magnetic material single nozzles to metalizationis in two parts, page width print should be used which are heads forlong normally held electromigration apart by a spring. lifetime and lowWhen the solenoid resistivity is actuated, the two Electroplating partsattract, is required displacing the ink. High saturation flux density isrequired (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz The Lorenzforce Low Force acts IJ06, IJ11, force acting on a current power as atwisting IJ13, IJ16 carrying wire in a consumption motion magnetic fieldis Many ink Typically, utilized. types can be only a quarter of Thisallows the used the solenoid magnetic field to Fast length provides besupplied operation force in a useful externally to the High directionprint head, for efficiency High local example with rare Easy currentsrequired earth permanent extension from Copper magnets. single nozzlesto metalization Only the current page width print should be usedcarrying wire need heads for long be fabricated on electromigration theprint head, lifetime and low simplifying resistivity materials Pigmentedrequirements. inks are usually infeasible Magneto- The actuator usesMany ink Force acts Fischenbeck, striction the giant types can be as atwisting U.S. Pat. No. magnetostrictive used motion 4,032,929 effect ofmaterials Fast Unusual IJ25 such as Terfenol-D operation materials suchas (an alloy of Easy Terfenol-D are terbium, extension from requireddysprosium and single nozzles to High local iron developed at page widthprint currents required the Naval heads Copper Ordnance High forcemetalization Laboratory, hence is available should be used Ter-Fe-NOL).For for long best efficiency, the electromigration actuator should belifetime and low pre-stressed to resistivity approx. 8 MPa. Pre-stressing may be required Surface Ink under positive Low RequiresSilverbrook, tension pressure is held in power supplementary EP 0771 658reduction a nozzle by surface consumption force to effect A2 and relatedtension. The Simple drop separation patent surface tension ofconstruction Requires applications the ink is reduced No special inkbelow the bubble unusual surfactants threshold, causing materials Speedmay the ink to egress required in be limited by from the nozzle.fabrication surfactant High properties efficiency Easy extension fromsingle nozzles to page width print heads Viscosity The ink viscositySimple Requires Silverbrook, reduction is locally reduced constructionsupplementary EP 0771 658 to select which No force to effect A2 andrelated drops are to be unusual drop separation patent ejected. Amaterials Requires applications viscosity reduction required in specialink can be achieved fabrication viscosity electrothermally Easyproperties with most inks, but extension from High special inks can besingle nozzles to speed is difficult engineered for a page width printto achieve 100:1 viscosity heads Requires reduction. oscillating inkpressure A high temperature difference (typically 80 degrees) isrequired Acoustic An acoustic wave Can Complex 1993 is generated andoperate without drive circuitry Hadimioglu et focussed upon the a nozzleplate Complex al, EUP 550,192 drop ejection fabrication 1993 region. LowElrod et al, EUP efficiency 572,220 Poor control of drop position Poorcontrol of drop volume Thermo- An actuator which Low Efficient IJ03,IJ09, elastic relies upon power aqueous IJ17, IJ18, IJ19, benddifferential consumption operation IJ20, IJ21, IJ22, actuator thermalexpansion Many ink requires a IJ23, IJ24, IJ27, upon Joule heating typescan be thermal insulator IJ28, IJ29, IJ30, is used. used on the hot sideIJ31, IJ32, IJ33, Simple Corrosion IJ34, IJ35, IJ36, planar preventioncan IJ37, IJ38, IJ39, fabrication be difficult IJ40, IJ41 Small chipPigmented area required for inks may be each actuator infeasible, asFast pigment particles operation may jam the High bend actuatorefficiency CMOS compatible voltages and currents Standard MEMS processescan be used Easy extension from single nozzles to page width print headsHigh CTE A material with a High force Requires IJ09, IJ17, thermo- veryhigh can be generated special material IJ18, IJ20, IJ21, elasticcoefficient of Three (e.g. PTFE) IJ22, IJ23, IJ24, actuator thermalexpansion methods of Requires a IJ27, IJ28, IJ29, (CTE) such as PTFEdeposition PTFE deposition IJ30, IJ31, IJ42, polytetrafluoroethylene areunder process, which is IJ43, IJ44 (PTFE) is development: not yetstandard used. As high CTE chemical vapor in ULSI fabs materials aredeposition PTFE usually non- (CVD), spin deposition conductive, acoating, and cannot be heater fabricated evaporation followed with froma conductive PTFE is a high temperature material is candidate for (above350° C.) incorporated. A 50 μm low dielectric processing long PTFEconstant Pigmented bend actuator with insulation in inks may bepolysilicon heater ULSI infeasible, as and 15 mW power Very low pigmentparticles input can provide power may jam the 180 μN force andconsumption bend actuator 10 μm deflection. Many ink Actuator motionstypes can be include: used Bend Simple Push planar Buckle fabricationRotate Small chip area required for each actuator Fast operation HighConductive A polymer with a High force Requires IJ24 polymer highcoefficient of can be generated special materials thermo- thermalexpansion Very low development elastic (such as PTFE) is power (High CTEactuator doped with consumption conductive conducting Many ink polymer)substances to types can be Requires a increase its used PTFE depositionconductivity to Simple process, which is about 3 orders of planar notyet standard magnitude below fabrication in ULSI fabs that of copper.The Small chip PTFE conducting area required for deposition polymerexpands each actuator cannot be when resistively Fast followed withheated. operation high temperature Examples of High (above 350° C.)conducting efficiency processing dopants include: CMOS EvaporationCarbon nanotubes compatible and CVD Metal fibers voltages and depositionConductive currents techniques polymers such as Easy cannot be useddoped extension from Pigmented polythiophene single nozzles to inks maybe Carbon granules page width print infeasible, as heads pigmentparticles may jam the bend actuator Shape A shape memory High forceFatigue IJ26 memory alloy such as TiNi is available limits maximum alloy(also known as (stresses of number of cycles Nitinol —Nickel hundreds ofLow strain Titanium alloy MPa) (1%) is required developed at the Largeto extend fatigue Naval Ordnance strain is resistance Laboratory) isavailable (more Cycle rate thermally switched than 3%) limited by heatbetween its weak High removal martensitic state corrosion Requires andits high resistance unusual stiffness austenitic Simple materials (TiNi)state. The shape of construction The latent the actuator in its Easyheat of martensitic state is extension from transformation deformedrelative single nozzles to must be to the austenitic page width printprovided shape. The shape heads High change causes Low current operationejection of a drop. voltage Requires operation pre-stressing to distortthe martensitic state Linear Linear magnetic Linear Requires IJ12Magnetic actuators include Magnetic unusual Actuator the Linearactuators can be semiconductor Induction Actuator constructed withmaterials such as (LIA), Linear high thrust, long soft magneticPermanent Magnet travel, and high alloys (e.g. Synchronous efficiencyusing CoNiFe) Actuator planar Some (LPMSA), Linear semiconductorvarieties also Reluctance fabrication require Synchronous techniquespermanent Actuator (LRSA), Long magnetic Linear Switched actuator travelis materials such as Reluctance available Neodymium iron Actuator(LSRA), Medium boron (NdFeB) and the Linear force is available RequiresStepper Actuator Low complex multi- (LSA). voltage phase drive operationcircuitry High current operation

BASIC OPERATION MODE Description Advantages Disadvantages ExamplesActuator This is the Simple Drop Thermal directly simplest mode ofoperation repetition rate is ink jet pushes operation: the No usuallylimited Piezoelectric ink actuator directly external fields to around 10kHz. ink jet supplies sufficient required However, IJ01, IJ02, kineticenergy to Satellite this is not IJ03, IJ04, IJ05, expel the drop. dropscan be fundamental to IJ06, IJ07, IJ09, The drop must avoided if dropthe method, but IJ11, IJ12, IJ14, have a sufficient velocity is less isrelated to the IJ16, IJ20, IJ22, velocity to than 4 m/s refill methodIJ23, IJ24, IJ25, overcome the Can be normally used IJ26, IJ27, IJ28,surface tension. efficient, All of the IJ29, IJ30, IJ31, depending upondrop kinetic IJ32, IJ33, IJ34, the actuator used energy must be IJ35,IJ36, IJ37, provided by the IJ38, IJ39, IJ40, actuator IJ41, IJ42, IJ43,Satellite IJ44 drops usually form if drop velocity is greater than 4.5m/s Proximity The drops to be Very Requires Silverbrook, printed aresimple print close proximity EP 0771 658 selected by some headfabrication between the A2 and related manner (e.g. can be used printhead and patent thermally induced The drop the print media applicationssurface tension selection means or transfer roller reduction of does notneed to May pressurized ink). provide the require two print Selecteddrops are energy required heads printing separated from the to separatethe alternate rows of ink in the nozzle drop from the the image bycontact with the nozzle Monolithic print medium or a color printtransfer roller. heads are difficult Electro- The drops to be VeryRequires Silverbrook, static pull printed are simple print very high EP0771 658 on ink selected by some head fabrication electrostatic field A2and related manner (e.g. can be used Electrostatic patent thermallyinduced The drop field for small applications surface tension selectionmeans nozzle sizes is Tone-Jet reduction of does not need to above airpressurized ink). provide the breakdown Selected drops are energyrequired Electrostatic separated from the to separate the field may inkin the nozzle drop from the attract dust by a strong electric nozzlefield. Magnetic The drops to be Very Requires Silverbrook, pull onprinted are simple print magnetic ink EP 0771 658 ink selected by somehead fabrication Ink colors A2 and related manner (e.g. can be usedother than black patent thermally induced The drop are difficultapplications surface tension selection means Requires reduction of doesnot need to very high pressurized ink). provide the magnetic fieldsSelected drops are energy required separated from the to separate theink in the nozzle drop from the by a strong nozzle magnetic field actingon the magnetic ink. Shutter The actuator High Moving IJ13, IJ17, movesa shutter to speed (>50 kHz) parts are IJ21 block ink flow to operationcan be required the nozzle. The ink achieved due to Requires pressure ispulsed reduced refill ink pressure at a multiple of the time modulatordrop ejection Drop Friction frequency. timing can be and wear must veryaccurate be considered The Stiction is actuator energy possible can bevery low Shuttered The actuator Actuators Moving IJ08, IJ15, grill movesa shutter to with small travel parts are IJ18, IJ19 block ink flow canbe used required through a grill to Actuators Requires the nozzle. Thewith small force ink pressure shutter movement can be used modulatorneed only be equal High Friction to the width of the speed (>50 kHz) andwear must grill holes. operation can be be considered achieved Stictionis possible Pulsed A pulsed magnetic Extremely Requires IJ10 magneticfield attracts an low energy an external pull on ‘ink pusher’ at theoperation is pulsed magnetic ink drop ejection possible field pusherfrequency. An No heat Requires actuator controls a dissipation specialmaterials catch, which problems for both the prevents the ink actuatorand the pusher from ink pusher moving when a Complex drop is not to beconstruction ejected.

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description AdvantagesDisadvantages Examples None The actuator Simplicity Drop Most inkdirectly fires the of construction ejection energy jets, including inkdrop, and there Simplicity must be supplied piezoelectric and is noexternal field of operation by individual thermal bubble. or other Smallnozzle actuator IJ01, IJ02, mechanism physical size IJ03, IJ04, IJ05,required. IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24, IJ25,IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36, IJ37,IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The ink pressureOscillating Requires Silverbrook, ink oscillates, ink pressure canexternal ink EP 0771 658 pressure providing much of provide a refillpressure A2 and related (including the drop ejection pulse, allowingoscillator patent acoustic energy. The higher operating Ink applicationsstimulation) actuator selects speed pressure phase IJ08, IJ13, whichdrops are to The and amplitude IJ15, IJ17, IJ18, be fired by actuatorsmay must be IJ19, IJ21 selectively operate with carefully blocking ormuch lower controlled enabling nozzles. energy Acoustic The ink pressureAcoustic reflections in the oscillation may be lenses can be ink chamberachieved by used to focus the must be vibrating the print sound on thedesigned for head, or preferably nozzles by an actuator in the inksupply. Media The print head is Low Precision Silverbrook, proximityplaced in close power assembly EP 0771 658 proximity to the Highrequired A2 and related print medium. accuracy Paper patent Selecteddrops Simple fibers may cause applications protrude from the print headproblems print head further construction Cannot than unselected print onrough drops, and contact substrates the print medium. The drop soaksinto the medium fast enough to cause drop separation. Transfer Drops areprinted High Bulky Silverbrook, roller to a transfer roller accuracyExpensive EP 0771 658 instead of straight Wide Complex A2 and related tothe print range of print construction patent medium. A substrates can beapplications transfer roller can used Tektronix also be used for Ink canbe hot melt proximity drop dried on the piezoelectric ink separation.transfer roller jet Any of the IJ series Electro- An electric field isLow Field Silverbrook, static used to accelerate power strength requiredEP 0771 658 selected drops Simple for separation of A2 and relatedtowards the print print head small drops is patent medium. constructionnear or above air applications breakdown Tone-Jet Direct A magneticfield is Low Requires Silverbrook, magnetic used to accelerate powermagnetic ink EP 0771 658 field selected drops of Simple Requires A2 andrelated magnetic ink print head strong magnetic patent towards the printconstruction field applications medium. Cross The print head is Does notRequires IJ06, IJ16 magnetic placed in a require magnetic externalmagnet field constant magnetic materials to be Current field. The Lorenzintegrated in the densities may be force in a current print head high,resulting in carrying wire is manufacturing electromigration used tomove the process problems actuator. Pulsed A pulsed magnetic Very lowComplex IJ10 magnetic field is used to power operation print head fieldcyclically attract a is possible construction paddle, which SmallMagnetic pushes on the ink. print head size materials A small actuatorrequired in print moves a catch, head which selectively prevents thepaddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator Operational Many Thermalmechanical simplicity actuator Bubble Ink jet amplification ismechanisms IJ01, IJ02, used. The actuator have insufficient IJ06, IJ07,IJ16, directly drives the travel, or IJ25, IJ26 drop ejectioninsufficient process. force, to efficiently drive the drop ejectionprocess Differential An actuator Provides High Piezoelectric expansionmaterial expands greater travel in stresses are IJ03, IJ09, bend more onone side a reduced print involved IJ17, IJ18, IJ19, actuator than on theother. head area Care must IJ20, IJ21, IJ22, The expansion be taken thatthe IJ23, IJ24, IJ27, may be thermal, materials do not IJ29, IJ30, IJ31,piezoelectric, delaminate IJ32, IJ33, IJ34, magnetostrictive, ResidualIJ35, IJ36, IJ37, or other bend resulting IJ38, IJ39, IJ42, mechanism.The from high IJ43, IJ44 bend actuator temperature or converts a highhigh stress force low travel during formation actuator mechanism to hightravel, lower force mechanism. Transient A trilayer bend Very good HighIJ40, IJ41 bend actuator where the temperature stresses are actuator twooutside layers stability involved are identical. This High Care mustcancels bend due speed, as a new be taken that the to ambient drop canbe fired materials do not temperature and before heat delaminateresidual stress. The dissipates actuator only Cancels responds toresidual stress of transient heating of formation one side or the other.Reverse The actuator loads Better Fabrication IJ05, IJ11 spring aspring. When the coupling to the complexity actuator is turned ink Highoff, the spring stress in the releases. This can spring reverse theforce/distance curve of the actuator to make it compatible with theforce/time requirements of the drop ejection. Actuator A series of thinIncreased Increased Some stack actuators are travel fabricationpiezoelectric ink stacked. This can Reduced complexity jets beappropriate drive voltage Increased IJ04 where actuators possibility ofrequire high short circuits due electric field to pinholes strength,such as electrostatic and piezoelectric actuators. Multiple Multiplesmaller Increases Actuator IJ12, IJ13, actuators actuators are used theforce forces may not IJ18, IJ20, IJ22, simultaneously to available fromadd linearly, IJ28, IJ42, IJ43 move the ink. Each an actuator reducingactuator need Multiple efficiency provide only a actuators can beportion of the positioned to force required. control ink flow accuratelyLinear A linear spring is Matches Requires IJ15 Spring used to transforma low travel print head area motion with small actuator with for thespring travel and high higher travel force into a longer requirementstravel, lower force Non- motion. contact method of motion transformationCoiled A bend actuator is Increases Generally IJ17, IJ21, actuatorcoiled to provide travel restricted to IJ34, IJ35 greater travel in aReduces planar reduced chip area. chip area implementations Planar dueto extreme implementations fabrication are relatively difficulty in easyto fabricate. other orientations. Flexure A bend actuator Simple Caremust IJ10, IJ19, bend has a small region means of be taken not to IJ33actuator near the fixture increasing travel exceed the point, whichflexes of a bend elastic limit in much more readily actuator the flexurearea than the remainder Stress of the actuator. distribution is Theactuator very uneven flexing is Difficult effectively to accuratelyconverted from an model with finite even coiling to an element analysisangular bend, resulting in greater travel of the actuator tip. Catch Theactuator Very low Complex IJ10 controls a small actuator energyconstruction catch. The catch Very small Requires either enables oractuator size external force disables movement Unsuitable of an inkpusher for pigmented that is controlled inks in a bulk manner. GearsGears can be used Low force, Moving IJ13 to increase travel low travelparts are at the expense of actuators can be required duration. Circularused Several gears, rack and Can be actuator cycles pinion, ratchets,fabricated using are required and other gearing standard surface Moremethods can be MEMS complex drive used. processes electronics Complexconstruction Friction, friction, and wear are possible Buckle A buckleplate can Very fast Must stay S. Hirata plate be used to change movementwithin elastic et al, “An Ink-jet a slow actuator achievable limits ofthe Head Using into a fast motion. materials for Diaphragm It can alsoconvert long device life Microactuator”, a high force, low High Proc.IEEE travel actuator into stresses involved MEMS, February a hightravel, Generally 1996, pp 418-423. medium force high power IJ18, IJ27motion. requirement Tapered A tapered Linearizes Complex IJ14 magneticmagnetic pole can the magnetic construction pole increase travel atforce/distance the expense of curve force. Lever A lever and MatchesHigh IJ32, IJ36, fulcrum is used to low travel stress around the IJ37transform a motion actuator with fulcrum with small travel higher traveland high force into requirements a motion with Fulcrum longer travel andarea has no lower force. The linear lever can also movement, and reversethe can be used for a direction of travel. fluid seal Rotary Theactuator is High Complex IJ28 impeller connected to a mechanicalconstruction rotary impeller. A advantage Unsuitable small angular Theratio for pigmented deflection of the of force to travel inks actuatorresults in of the actuator a rotation of the can be matched impellervanes, to the nozzle which push the ink requirements by againststationary varying the vanes and out of number of the nozzle. impellervanes Acoustic A refractive or No Large area 1993 lens diffractive (e.g.moving parts required Hadimioglu et zone plate) Only al, EUP 550,192acoustic lens is relevant for 1993 used to concentrate acoustic ink jetsElrod et al, EUP sound waves. 572,220 Sharp A sharp point is SimpleDifficult Tone-jet conductive used to concentrate construction tofabricate point an electrostatic using standard field. VLSI processesfor a surface ejecting ink-jet Only relevant for electrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the Simple High Hewlett- expansion actuator changes,construction in energy is Packard Thermal pushing the ink in the case oftypically Ink jet all directions. thermal ink jet required to Canonachieve volume Bubblejet expansion. This leads to thermal stress,cavitation, and kogation in thermal ink jet implementations Linear, Theactuator Efficient High IJ01, IJ02, normal to moves in a coupling to inkfabrication IJ04, IJ07, IJ11, chip direction normal to drops ejectedcomplexity may IJ14 surface the print head normal to the be required tosurface. The surface achieve nozzle is typically perpendicular in theline of motion movement. Parallel to The actuator Suitable FabricationIJ12, IJ13, chip moves parallel to for planar complexity IJ15, IJ33,,IJ34, surface the print head fabrication Friction IJ35, IJ36 surface.Drop Stiction ejection may still be normal to the surface. Membrane Anactuator with a The Fabrication 1982 push high force but effective areaof complexity Howkins U.S. Pat. No. small area is used the actuatorActuator 4,459,601 to push a stiff becomes the size membrane that ismembrane area Difficulty in contact with the of integration in ink. aVLSI process Rotary The actuator Rotary Device IJ05, IJ08, causes therotation levers may be complexity IJ13, IJ28 of some element, used toincrease May have such a grill or travel friction at a pivot impellerSmall chip point area requirements Bend The actuator bends A veryRequires 1970 when energized. small change in the actuator to be Kyseret al U.S. Pat. No. This may be due to dimensions can made from at3,946,398 differential be converted to a least two distinct 1973 thermalexpansion, large motion. layers, or to have Stemme U.S. Pat. No.piezoelectric a thermal 3,747,120 expansion, difference across IJ03,IJ09, magnetostriction, the actuator IJ10, IJ19, IJ23, or other form ofIJ24, IJ25, IJ29, relative IJ30, IJ31, IJ33, dimensional IJ34, IJ35change. Swivel The actuator Allows Inefficient IJ06 swivels around aoperation where coupling to the central pivot. This the net linear inkmotion motion is suitable force on the where there are paddle is zeroopposite forces Small chip applied to opposite area sides of the paddle,requirements e.g. Lorenz force. Straighten The actuator is Can beRequires IJ26, IJ32 normally bent, and used with shape careful balancestraightens when memory alloys of stresses to energized. where theensure that the austenitic phase quiescent bend is is planar accurateDouble The actuator bends One Difficult IJ36, IJ37, bend in onedirection actuator can be to make the IJ38 when one element used topower drops ejected by is energized, and two nozzles. both bend bendsthe other Reduced directions way when another chip size. identical.element is Not A small energized. sensitive to efficiency loss ambientcompared to temperature equivalent single bend actuators. ShearEnergizing the Can Not 1985 actuator causes a increase the readilyFishbeck U.S. Pat. No. shear motion in the effective travel applicableto 4,584,590 actuator material. of piezoelectric other actuatoractuators mechanisms Radial The actuator Relatively High force 1970constriction squeezes an ink easy to fabricate required Zoltan U.S. Pat.No. reservoir, forcing single nozzles Inefficient 3,683,212 ink from afrom glass Difficult constricted nozzle. tubing as to integrate withmacroscopic VLSI processes structures Coil/ A coiled actuator Easy toDifficult IJ17, IJ21, uncoil uncoils or coils fabricate as a tofabricate for IJ34, IJ35 more tightly. The planar VLSI non-planar motionof the free process devices end of the actuator Small area Poor out-ejects the ink. required, of-plane stiffness therefore low cost Bow Theactuator bows Can Maximum IJ16, IJ18, (or buckles) in the increase thetravel is IJ27 middle when speed of travel constrained energized.Mechanically High force rigid required Push-Pull Two actuators The NotIJ18 control a shutter. structure is readily suitable One actuator pullspinned at both for ink jets the shutter, and the ends, so has a whichdirectly other pushes it. high out-of- push the ink plane rigidity CurlA set of actuators Good fluid Design IJ20, IJ42 inwards curl inwards toflow to the complexity reduce the volume region behind of ink that theythe actuator enclose. increases efficiency Curl A set of actuatorsRelatively Relatively IJ43 outwards curl outwards, simple large chiparea pressurizing ink in construction a chamber surrounding theactuators, and expelling ink from a nozzle in the chamber. Iris Multiplevanes High High IJ22 enclose a volume efficiency fabrication of ink.These Small chip complexity simultaneously area Not rotate, reducingsuitable for the volume pigmented inks between the vanes. Acoustic Theactuator The Large area 1993 vibration vibrates at a high actuator canbe required for Hadimioglu et frequency. physically efficient al, EUP550,192 distant from the operation at 1993 ink useful Elrod et al, EUPfrequencies 572,220 Acoustic coupling and crosstalk Complex drivecircuitry Poor control of drop volume and position None In various inkjet No Various Silverbrook, designs the moving parts other tradeoffs EP0771 658 actuator does not are required to A2 and related move.eliminate patent moving parts applications Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal Fabrication Low speed Thermal tension waythat ink jets simplicity Surface ink jet are refilled. After Operationaltension force Piezoelectric the actuator is simplicity relatively smallink jet energized, it compared to IJ01-IJ07, typically returns actuatorforce IJ10-IJ14, IJ16, rapidly to its Long refill IJ20, IJ22-IJ45 normalposition. time usually This rapid return dominates the sucks in airtotal repetition through the nozzle rate opening. The ink surfacetension at the nozzle then exerts a small force restoring the meniscusto a minimum area. This force refills the nozzle. Shuttered Ink to thenozzle High Requires IJ08, IJ13, oscillating chamber is speed common inkIJ15, IJ17, IJ18, ink provided at a Low pressure IJ19, IJ21 pressurepressure that actuator energy, oscillator oscillates at twice as theactuator May not the drop ejection need only open be suitable forfrequency. When a or close the pigmented inks drop is to be shutter,instead ejected, the shutter of ejecting the is opened for 3 ink drophalf cycles: drop ejection, actuator return, and refill. The shutter isthen closed to prevent the nozzle chamber emptying during the nextnegative pressure cycle. Refill After the main High Requires IJ09actuator actuator has speed, as the two independent ejected a drop anozzle is actuators per second (refill) actively refilled nozzleactuator is energized. The refill actuator pushes ink into the nozzlechamber. The refill actuator returns slowly, to prevent its return fromemptying the chamber again. Positive The ink is held a High refillSurface Silverbrook, ink slight positive rate, therefore a spill must beEP 0771 658 pressure pressure. After the high drop prevented A2 andrelated ink drop is ejected, repetition rate is Highly patent the nozzlepossible hydrophobic applications chamber fills print head Alternativequickly as surface surfaces are for:, IJ01-IJ07, tension and inkrequired IJ10-IJ14, IJ16, pressure both IJ20, IJ22-IJ45 operate torefill the nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet Design Restricts Thermalchannel channel to the simplicity refill rate ink jet nozzle chamber isOperational May result Piezoelectric made long and simplicity in arelatively ink jet relatively narrow, Reduces large chip area IJ42, IJ43relying on viscous crosstalk Only drag to reduce partially inletback-flow. effective Positive The ink is under a Drop Requires aSilverbrook, ink positive pressure, selection and method (such as EP0771 658 pressure so that in the separation forces a nozzle rim or A2and related quiescent state can be reduced effective patent some of theink Fast refill hydrophobizing, applications drop already time or both)to Possible protrudes from the prevent flooding operation of the nozzle.of the ejection following: IJ01-IJ07, This reduces the surface of theIJ09-IJ12, pressure in the print head. IJ14, IJ16, IJ20, nozzle chamberIJ22,, IJ23-IJ34, which is required IJ36-IJ41, IJ44 to eject a certainvolume of ink. The reduction in chamber pressure results in a reductionin ink pushed out through the inlet. Baffle One or more The refillDesign HP baffles are placed rate is not as complexity Thermal Ink Jetin the inlet ink restricted as the May Tektronix flow. When the longinlet increase piezoelectric ink actuator is method. fabrication jetenergized, the Reduces complexity (e.g. rapid ink crosstalk Tektronixhot movement creates melt eddies which Piezoelectric restrict the flowprint heads). through the inlet. The slower refill process isunrestricted, and does not result in eddies. Flexible In this methodSignificantly Not Canon flap recently disclosed reduces back- applicableto restricts by Canon, the flow for edge- most ink jet inlet expandingactuator shooter thermal configurations (bubble) pushes on ink jetdevices Increased a flexible flap that fabrication restricts the inlet.complexity Inelastic deformation of polymer flap results in creep overextended use Inlet filter A filter is located Additional Restricts IJ04,IJ12, between the ink advantage of ink refill rate IJ24, IJ27, IJ29,inlet and the filtration May result IJ30 nozzle chamber. Ink filter incomplex The filter has a may be construction multitude of smallfabricated with holes or slots, no additional restricting ink processsteps flow. The filter also removes particles which may block thenozzle. Small The ink inlet Design Restricts IJ02, IJ37, inlet channelto the simplicity refill rate IJ44 compared nozzle chamber May result tonozzle has a substantially in a relatively smaller cross large chip areasection than that of Only the nozzle, partially resulting in easiereffective ink egress out of the nozzle than out of the inlet. Inlet Asecondary Increases Requires IJ09 shutter actuator controls speed of theink- separate refill the position of a jet print head actuator andshutter, closing off operation drive circuit the ink inlet when the mainactuator is energized. The inlet The method avoids Back-flow RequiresIJ01, IJ03, is located the problem of problem is careful design to 1J05,IJ06, IJ07, behind inlet back-flow by eliminated minimize the IJ10,IJ11, IJ14, the ink- arranging the ink- negative IJ16, IJ22, IJ23,pushing pushing surface of pressure behind IJ25, IJ28, IJ31, surface theactuator the paddle IJ32, IJ33, IJ34, between the inlet IJ35, IJ36,IJ39, and the nozzle. IJ40, IJ41 Part of The actuator and a SignificantSmall IJ07, IJ20, the wall of the ink reductions in increase in IJ26,IJ38 actuator chamber are back-flow can be fabrication moves to arrangedso that achieved complexity shut off the motion of the Compact the inletactuator closes off designs possible the inlet. Nozzle In some Ink back-None Silverbrook, actuator configurations of flow problem is related toink EP 0771 658 does not ink jet, there is no eliminated back-flow on A2and related result in expansion or actuation patent ink back- movementof an applications flow actuator which Valve-jet may cause ink Tone-jetback-flow through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles No added May not Most ink nozzle are firedcomplexity on be sufficient to jet systems firing periodically, theprint head displace dried IJ01, IJ02, before the ink has ink IJ03, IJ04,IJ05, a chance to dry. IJ06, IJ07, IJ09, When not in use IJ10, IJ11,IJ12, the nozzles are IJ14, IJ16, IJ20, sealed (capped) IJ22, IJ23,IJ24, against air. IJ25, IJ26, IJ27, The nozzle firing IJ28, IJ29, IJ30,is usually IJ31, IJ32, IJ33, performed during a IJ34, IJ36, IJ37,special clearing IJ38, IJ39, IJ40,, cycle, after first IJ41, IJ42, IJ43,moving the print IJ44,, IJ45 head to a cleaning station. Extra Insystems which Can be Requires Silverbrook, power to heat the ink, but dohighly effective higher drive EP 0771 658 ink heater not boil it underif the heater is voltage for A2 and related normal situations, adjacentto the clearing patent nozzle clearing can nozzle May applications beachieved by require larger over-powering the drive transistors heaterand boiling ink at the nozzle. Rapid The actuator is Does notEffectiveness May be succession fired in rapid require extra dependsused with: IJ01, of succession. In drive circuits on substantially IJ02,IJ03, IJ04, actuator some the print head upon the IJ05, IJ06, IJ07,pulses configurations, this Can be configuration of IJ09, IJ10, IJ11,may cause heat readily the ink jet nozzle IJ14, IJ16, IJ20, build-up atthe controlled and IJ22, IJ23, IJ24, nozzle which boils initiated byIJ25, IJ27, IJ28, the ink, clearing digital logic IJ29, IJ30, IJ31, thenozzle. In other IJ32, IJ33, IJ34, situations, it may IJ36, IJ37, IJ38,cause sufficient IJ39, IJ40, IJ41, vibrations to IJ42, IJ43, IJ44,dislodge clogged IJ45 nozzles. Extra Where an actuator A simple Not Maybe power to is not normally solution where suitable where used with:IJ03, ink driven to the limit applicable there is a hard IJ09, IJ16,IJ20, pushing of its motion, limit to actuator IJ23, IJ24, IJ25,actuator nozzle clearing movement IJ27, IJ29, IJ30, may be assisted byIJ31, IJ32, IJ39, providing an IJ40, IJ41, IJ42, enhanced drive IJ43,IJ44, IJ45 signal to the actuator. Acoustic An ultrasonic A high HighIJ08, IJ13, resonance wave is applied to nozzle clearing implementationIJ15, IJ17, IJ18, the ink chamber. capability can be cost if systemIJ19, IJ21 This wave is of an achieved does not already appropriate Maybe include an amplitude and implemented at acoustic actuator frequencyto cause very low cost in sufficient force at systems which the nozzleto clear already include blockages. This is acoustic easiest to achieveactuators if the ultrasonic wave is at a resonant frequency of the inkcavity. Nozzle A microfabricated Can clear Accurate Silverbrook,clearing plate is pushed severely clogged mechanical EP 0771 658 plateagainst the nozzles alignment is A2 and related nozzles. The platerequired patent has a post for Moving applications every nozzle. A partsare post moves required through each There is nozzle, displacing risk ofdamage dried ink. to the nozzles Accurate fabrication is required InkThe pressure of the May be Requires May be pressure ink is temporarilyeffective where pressure pump used with all IJ pulse increased so thatother methods or other pressure series ink jets ink streams from cannotbe used actuator all of the nozzles. Expensive This may be used Wastefulin conjunction of ink with actuator energizing. Print A flexible ‘blade’Effective Difficult Many ink head is wiped across the for planar printto use if print jet systems wiper print head surface. head surfaces headsurface is The blade is Low cost non-planar or usually fabricated veryfragile from a flexible Requires polymer, e.g. mechanical parts rubberor synthetic Blade can elastomer. wear out in high volume print systemsSeparate A separate heater Can be Fabrication Can be ink is provided atthe effective where complexity used with many boiling nozzle althoughother nozzle IJ series ink jets heater the normal drop clearing methodsejection cannot be used mechanism does Can be not require it. Theimplemented at heaters do not no additional require individual cost insome ink drive circuits, as jet many nozzles can configurations becleared simultaneously, and no imaging is required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages ExamplesElectro- A nozzle plate is Fabrication High Hewlett formed separatelysimplicity temperatures and Packard Thermal nickel fabricated frompressures are Ink jet electroformed required to bond nickel, and bondednozzle plate to the print head Minimum chip. thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks Eachhole Canon ablated or holes are ablated required must be Bubblejetdrilled by an intense UV Can be individually 1988 polymer laser in anozzle quite fast formed Sercel et al., plate, which is Some SpecialSPIE, Vol. 998 typically a control over equipment Excimer Beam polymersuch as nozzle profile is required Applications, pp. polyimide orpossible Slow 76-83 polysulphone Equipment where there are 1993 requiredis many thousands Watanabe et al., relatively low of nozzles per U.S.Pat. No. 5,208,604 cost print head May produce thin burrs at exit holesSilicon A separate nozzle High Two part K. Bean, micro- plate isaccuracy is construction IEEE machined micromachined attainable Highcost Transactions on from single crystal Requires Electron silicon, andprecision Devices, Vol. bonded to the print alignment ED-25, No. 10,head wafer. Nozzles 1978, pp 1185-1195 may be clogged Xerox by adhesive1990 Hawkins et al., U.S. Pat. No. 4,899,181 Glass Fine glass No Verysmall 1970 capillaries capillaries are expensive nozzle sizes are ZoltanU.S. Pat. No. drawn from glass equipment difficult to form 3,683,212tubing. This required Not suited method has been Simple to for mass usedfor making make single production individual nozzles, nozzles but isdifficult to use for bulk manufacturing of print heads with thousands ofnozzles. Monolithic, The nozzle plate is High Requires Silverbrook,surface deposited as a accuracy (<1 μm) sacrificial layer EP 0771 658micro- layer using Monolithic under the nozzle A2 and related machinedstandard VLSI Low cost plate to form the patent using depositionExisting nozzle chamber applications VLSI techniques. processes can beSurface IJ01, IJ02, litho- Nozzles are etched used may be fragile toIJ04, IJ11, IJ12, graphic in the nozzle plate the touch IJ17, IJ18,IJ20, processes using VLSI IJ22, IJ24, IJ27, lithography and IJ28, IJ29,IJ30, etching. IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is High RequiresIJ03, IJ05, etched a buried etch stop accuracy (<1 μm) long etch timesIJ06, IJ07, IJ08, through in the wafer. Monolithic Requires a IJ09,IJ10, IJ13, substrate Nozzle chambers Low cost support wafer IJ14, IJ15,IJ16, are etched in the No IJ19, IJ21, IJ23, front of the wafer,differential IJ25, IJ26 and the wafer is expansion thinned from thebackside. Nozzles are then etched in the etch stop layer. No nozzleVarious methods No Difficult Ricoh plate have been tried to nozzles toto control drop 1995 Sekiya et al eliminate the become clogged positionU.S. Pat. No. 5,412,413 nozzles entirely, to accurately 1993 preventnozzle Crosstalk Hadimioglu et al clogging. These problems EUP 550,192include thermal 1993 bubble Elrod et al EUP mechanisms and 572,220acoustic lens mechanisms Trough Each drop ejector Reduced Drop IJ35 hasa trough manufacturing firing direction through which a complexity issensitive to paddle moves. Monolithic wicking. There is no nozzle plate.Nozzle slit The elimination of No Difficult 1989 Saito instead of nozzleholes and nozzles to to control drop et al U.S. Pat. No. individualreplacement by a become clogged position 4,799,068 nozzles slitencompassing accurately many actuator Crosstalk positions reducesproblems nozzle clogging, but increases crosstalk due to ink surfacewaves

DROP EJECTION DIRECTION Description Advantages Disadvantages ExamplesEdge Ink flow is along Simple Nozzles Canon (‘edge the surface of theconstruction limited to edge Bubblejet 1979 shooter’) chip, and inkdrops No silicon High Endo et al GB are ejected from etching requiredresolution is patent 2,007,162 the chip edge. Good heat difficult Xeroxsinking via Fast color heater-in-pit substrate printing requires 1990Hawkins et Mechanically one print head al U.S. Pat. No. strong per color4,899,181 Ease of Tone-jet chip handing Surface Ink flow is along Nobulk Maximum Hewlett- (‘roof the surface of the silicon etching ink flowis Packard TIJ shooter’) chip, and ink drops required severely 1982Vaught et are ejected from Silicon restricted al U.S. Pat. No. the chipsurface, can make an 4,490,728 normal to the effective heat IJ02, IJ11,plane of the chip. sink IJ12, IJ20, IJ22 Mechanical strength Through Inkflow is through High ink Requires Silverbrook, chip, the chip, and inkflow bulk silicon EP 0771 658 forward drops are ejected Suitable etchingA2 and related (‘up from the front for pagewidth patent shooter’)surface of the chip. print heads applications High IJ04, IJ17, nozzlepacking IJ18, IJ24, IJ27-IJ45 density therefore low manufacturing costThrough Ink flow is through High ink Requires IJ01, IJ03, chip, thechip, and ink flow wafer thinning IJ05, IJ06, IJ07, reverse drops areejected Suitable Requires IJ08, IJ09, IJ10, (‘down from the rear forpagewidth special handling IJ13, IJ14, IJ15, shooter’) surface of thechip. print heads during IJ16, IJ19, IJ21, High manufacture IJ23, IJ25,IJ26 nozzle packing density therefore low manufacturing cost Through Inkflow is through Suitable pagewidth Epson actuator the actuator, whichfor piezoelectric print heads Stylus is not fabricated as print headsrequire several Tektronix part of the same thousand hot melt substrateas the connections to piezoelectric ink drive transistors. drivecircuits jets Cannot be manufactured in standard CMOS fabs Complexassembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Waterbased ink Environmentally Slow Most dye which typically friendly dryingexisting ink jets contains: water, No odor Corrosive All IJ dye,surfactant, Bleeds on series ink jets humectant, and paper Silverbrook,biocide. May EP 0771 658 Modern ink dyes strikethrough A2 and relatedhave high water- Cockles patent fastness, light paper applicationsfastness Aqueous, Water based ink Environmentally Slow IJ02, IJ04,pigment which typically friendly drying IJ21, IJ26, IJ27, contains:water, No odor Corrosive IJ30 pigment, Reduced Pigment Silverbrook,surfactant, bleed may clog EP 0771 658 humectant, and Reduced nozzles A2and related biocide. wicking Pigment patent Pigments have an Reduced mayclog applications advantage in strikethrough actuator Piezoelectricreduced bleed, mechanisms ink-jets wicking and Cockles Thermalstrikethrough. paper ink jets (with significant restrictions) Methyl MEKis a highly Very fast Odorous All IJ Ethyl volatile solvent dryingFlammable series ink jets Ketone used for industrial Prints on (MEK)printing on various difficult surfaces substrates such such as aluminumas metals and cans. plastics Alcohol Alcohol based inks Fast Slight AllIJ (ethanol, can be used where drying odor series ink jets 2-butanol,the printer must Operates Flammable and operate at at sub-freezingothers) temperatures temperatures below the freezing Reduced point ofwater. An paper cockle example of this is Low cost in-camera consumerphotographic printing. Phase The ink is solid at No drying HighTektronix change room temperature, time-ink viscosity hot melt (hotmelt) and is melted in instantly freezes Printed ink piezoelectric inkthe print head on the print typically has a jets before jetting. Hotmedium ‘waxy’ feel 1989 melt inks are Almost Printed Nowak U.S. Pat. No.usually wax based, any print pages may 4,820,346 with a melting mediumcan be ‘block’ All IJ point around 80° C.. used Ink series ink jetsAfter jetting No paper temperature may the ink freezes cockle occurs beabove the almost instantly No curie point of upon contacting wickingoccurs permanent the print medium No bleed magnets or a transfer roller.occurs Ink heaters No consume power strikethrough Long occurs warm-uptime Oil Oil based inks are High High All IJ extensively used insolubility viscosity: this is series ink jets offset printing. mediumfor a significant They have some dyes limitation for use advantages inDoes not in ink jets, which improved cockle paper usually require acharacteristics on Does not low viscosity. paper (especially wickthrough Some short no wicking or paper chain and multi- cockle). Oilbranched oils soluble dies and have a pigments are sufficiently lowrequired. viscosity. Slow drying Micro- A microemulsion Stops inkViscosity All IJ emulsion is a stable, self bleed higher than series inkjets forming emulsion High dye water of oil, water, and solubility Costis surfactant. The Water, oil, slightly higher characteristic drop andamphiphilic than water based size is less than soluble dies can ink 100nm, and is be used High determined by the Can surfactant preferredcurvature stabilize pigment concentration of the surfactant. suspensionsrequired (around 5%)

1. An inkjet nozzle arrangement comprising: a wafer defining an inkchamber for holding ink; a chamber roof covering the ink chamber, thechamber roof comprising: an ink ejection port supported by a pluralityof outwardly extending bridge members; and a plurality of elongateheater elements interleaved between the bridge members for causingejection of ink held in the ink chamber through the ink ejection port.2. A nozzle arrangement as claimed in claim 1, wherein the heaterelements are arranged to be generally circular and comprises a pluralityof spaced apart serpentine stations which extend radially inward.
 3. Anozzle arrangement as claimed in claim 2, wherein each serpentinestation is symmetric and comprises a mirrored pair of serpentineportions.
 4. A nozzle arrangement as claimed in claim 1, wherein theends of the heater elements terminate in a pair of vias which areconnected to a metal layer of the wafer.
 5. A nozzle arrangement asclaimed in claim 1, wherein the ink chamber is generally funnel-shapedand tapers inwardly away from the chamber roof.
 6. A nozzle arrangementas claimed in claim 5, wherein the wafer further defines an ink supplyinlet at an apex of the tapered ink chamber, the ink supply inlet beingsubstantially aligned with the ink ejection port.
 7. A nozzlearrangement as claimed in claim 1, wherein each bridge member defines anink flow guide rail.